This invention relates to a combination weigher and, especially, to a combination weigher having auxiliary hoppers.
FIGS. 1(a) and 1(b) show a specific arrangement of mechanical components of a prior art combination weigher, which is suggested, for example, in the Japanese patent opening gazette No. 58-41326. In the drawings, a plurality of electromagnetic feeders 4 are radially arranged around a dispersion feeder 2 and a feed hopper 6 is disposed under the distal end of each electromagnetic feeder 4. A weigh hopper 8 is disposed under each feed hopper 6 and an auxiliary hopper 10 is disposed under each weigh hopper 8. The feed, weigh and auxiliary hoppers 6, 8 and 10 are respectively arranged annularly in concentric fashion. Each weigh hopper 8 has an outer gate 12a for discharging product directly downward and an inner gate 12b for feeding product into the underlying auxiliary hopper 10. Accordingly, the auxiliary hoppers 10 are arranged annularly under the inner gates 12b. A collection chute 14 is disposed under the auxiliary hoppers 10 for collecting product discharged from weigh hoppers 8 and/or auxiliary hoppers 10. Each auxiliary hopper 10 has a discharge gate 16 adapted to open inwardly as shown in phantom 16' and each feed hopper 6 also has a similar discharge gate 18.
However, a combination weigher with the aforementioned arrangement of weigh hoppers 8 and auxiliary hoppers 10 requires a collection chute of relatively large diameter at its upper end. On the one hand, assuming the gate 16' of each auxiliary hopper 10 has a width b1 as shown in FIG. 1b, the auxiliary hoppers must be positioned so that the lower edges of the opened gates 16' never project inwardly beyond a corresponding regular polygon having a side length b1, in order to ensure that the gate 16' of each hopper may open without any interference from the other gates 16. On the other hand, since each auxiliary hopper 10 is disposed directly under the inner gate 12b of a corresponding weigh hopper 8, the collection chute 14 must have a diameter sufficiently large to completely collect the product discharged from the outer gates 12a of weigh hoppers 8. In the prior art combination weigher, such a bulky collection chute has resulted not only in an increased overall machine size and a corresponding increase in the area occupied by the machine, but also in substantial difficulty in maintenance service. While the gate width b1 may be reduced to remove the above-mentioned problem, this will result in reduction of the flow rate of product which causes undesirable reduction in machine efficiency. Although the flow rate can be maintained by increasing the height of gate 16, this will result in undesirable increase in the machine height.